Fun With var

A live-coding talk where I show off all you need to know about var in Java. And then some.

Since Java 10 you can use var to let the compiler infer a local variable's type:

var users = new ArrayList<User>();

And that's pretty much it, right? Surprisingly, no! There are a lot of details to consider...

  • is this JavaScript?!
  • how exactly is the type inferred?
  • where can I use var and what should I look out for?
  • won't this lead to unreadable code?

... and a few fun things to do with var...

  • playing with anonymous classes (don't!)
  • faking traits (don't!)
  • faking intersection types (do!)

After this live-coding deep dive into var, you'll know all about Java 10's flagship feature.


Here's the current version of the slides.

I also embedded them below. If they're focussed, you can navigate with arrow keys or swipes (they're two-dimensional, with chapters on the horizontal axis and chapter content layed out vertically). Use Page Up/Down for linearized order and ? for more shortcuts.


Here's a good recording of the talk. I hope you'll like it.

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Watch on YouTube

Past Presentations

I gave this talk a few times before. See below for links to slides (as they were at that very event), videos, and other information.